The belt driven tape cartridge of U.S. Pat. No. 3,692,255 has been very successfully utilized to interface with computers where rapid acceleration and deceleration of the tape are required. However, because the drive belt has a finite thickness, when the supply reel has a small amount of tape the belt must pass through a sharper radius and thus produces a larger tension in the tape than when the supply reel has a greater amount of tape. Also, when the tape supply is small the angle of wrap around the adjacent tape guide is larger which creates a larger tape tension than when the supply is large and the wrap around the guide is thus smaller. These two effects are additive and make the tape tension at the transducer nonuniform as the tape is transferred between the reels. This is undesirable because a certain minimum tape tension is desired to maintain good contact with the transducer but a greater tape tension is undesirable since it increases the wear on the transducer.